1. Field of the Invention
The present invention relates generally to private local networks, and more specifically to a private local switching system for an Integrated Services Digital Network (ISDN).
2. Description of the Related Art
In the ISDN networks, user packets are transmitted either at the basic rate of 64 kbps on a B-channel (bearer service) or at 16 kpbs on a control channel or D-channel. The packets transmitted on B- and D-channels are referred to as B-channel and D-channel packets, respectively. D-channel packets can be transmitted as a packet-mode signal or as a signaling message. In the current ISDN private branch exchange, the D-channel packets, either packet mode or signaling, are passed to a controller that provides overall control of the PBX including the switch. The signaling message is processed by the controller and then transmitted, as necessary, to the network. The same process occurs in the opposite direction for incoming D-channel packets from the network. One disadvantage of the current PBX is that, since the controller is designed to process signaling messages, the traffic of D-channel packet mode signals imposes an additional load on the controller. Thus, it is highly likely that the total traffic load of the system easily exceeds the capacity of the controller if the D-channel packet mode traffic increases significantly, and as a result, the switching performance of the PBX is severely affected.